Urine is also important not only because it represents quantitatively
a major vehicle for water excretion by the pig, but also because urine
fl ow is the main mechanism for regulation of water output, controlled by
aldosterone and arginine vasopressin (antidiuretic hormone) as well as by
solute load (Robertson and Norgaard, 2002). Just as drinking water can
be regulated to maintain necessary intake, urine output can be regulated
to maintain necessary water removal from the body. Because dehydration
and overhydration can be fatal, exquisitely sensitive mechanisms are present
to ensure that a tight water balance is maintained